(1) Field of the Invention
This invention relates to a speech-path switch for establishing and terminating connection between a subscriber's line and a trunk in a switching system of a mobile communication device.
(2) Description of the Related Art
A switching system has speech-path switches for establishing and terminating connection between subscriber's lines and trunks.
The speech-path switch comprises a plurality of input and output ports.
Each input port is connected to one end of a subscriber's line. The other end of the subscriber's line is connected to a terminal of a subscriber. On the other hand, each output port is connected to one end of a trunk. The other end of the trunk is connected to another switching system. The output port is also connected to one end of a transmitting and receiving line. The other end of the transmitting and receiving line is connected to a communication servicing device. The communication servicing device provides communication services to the associated terminals. Such services include call waiting which allows breaking into a call temporarily to leave a quick voice message to a terminal.
On receiving a call establishment request signal from another terminal, the switching system determines a switching network in which a called or destination terminal is contained. The switching system also determines the output port of the trunk connected to the destination switching system in the switch network.
The switching system examines the speech-path switch and the available paths to which the call is routed, determines and which of these is free. The switching system sets up a speech-path between the input port of the subscriber's line to be connected to the terminal and the output port of the trunk to be connected to the calling switch.
On receiving a communication service request from the terminal in communication, the switching system determines which communication service is requested by the terminal. In addition, the switching system also determines the associated communication servicing device and the output port of the transmitting and receiving line connected thereto. The switching system terminates the connection between the input port of the subscriber's line and the output port of the trunk. At the same time, the switching system establishes the connection between the input port of the subscriber's line and the output port of the transmitting and receiving line.
A communication network may sometimes contain a mobile device that transmits and receives data using radio waves. Such communication network is provided with a plurality of base stations between the switching systems and the mobile device. The base station transmits and receives data using radio waves to and from the mobile device in a specific area. In addition, the base station transmits and receives data using wires including the subscriber's lines to and from switching systems.
For example, a base station covering a specific zone A transmits, when receiving a call establishment request from a mobile device located within the specific zone A, a call establishment request signal to the switching system through the subscriber's line.
In response to the call establishment request signal, the switching system determines the input port of the subscriber's line connected to the base station A. The switching system determines a switching system covering the called mobile device as well as the output port of the trunk connected to the destination switching system.
Subsequently, the switching system finds available paths in the speech-path switch and establishes a speech-path between the input port and the output port. In addition, the switching system transmits the call establishment request signal to the called switching system through the speech-path and the trunk.
When the mobile device in communication moves out of the specific zone A to a specific zone B, a base station B covering the specific zone B notifies the switching system of the movement of the mobile device.
In response to the notification of the movement of the mobile device, the switching system terminates the speech-path established before the movement. Subsequently, the switching system finds available paths in the speech-path switch and establishes a fresh speech-path between the input port of the subscriber's line connected to the station B and the output port of the trunk.
In addition, on receiving a request for the communication service from the mobile device, the switching system terminates the path established between the input port of the subscriber and the output port of the trunk. The switching system determines the communication servicing device corresponding to the communication service in question. At the same time, the switching system determines the output port of the transmitting and receiving line connected to the destined communication servicing device. The switching system confirms the busy states of the paths in the speech-path switch, and also confirms which of these is free. The switching system then establishes the speech-path between the input port of the subscriber's line and the output port of the transmitting and receiving line.
A method of switching speech-paths is now described in detail.
An audio source is described here as an example of the communication servicing device. The audio source is a device for transmitting a voice message to the mobile device.
Before setting up communication, a user of the mobile device located in the specific zone A sends an. off-hook signal and calls a called number of the destination telephone terminal.
In response to the off-hook signal and the called number, the base station covering the specific zone A sends these signals to the switching system of the mobile device.
The switching system analyzes the called number to determine the switching network in which the called telephone terminal is contained. The switching system traps the trunk connected to the switching system in the destined switching network.
The speech-path switch establishes a first speech-path between the input port connected to the subscriber's line and the output port connected to the trunk. At this time, the mobile device and the destination telephone terminal are in a communication state.
If the called telephone terminal receives an interruption call in the communication between the mobile device, the mobile device is in the call waiting (to wait until termination of the other call). In this event, the speech-path switch establishes a second speech-path between the line connected to the audio source and the subscriber's line.
If the mobile device in communication or in call waiting moves out of the specific zone A to the specific zone B, the base station covering the specific zone B notifies the switching system of the movement of the mobile device.
In response to the notification of the movement of the mobile device, the switching system terminates the first speech-path and, at the same time, establishes a third speech-path between the subscriber's line connected to the base station covering the specific zone B and the trunk or between the subscriber's line connected to the base station covering the specific zone B and the transmitting and receiving line connected to the audio source.
Upon termination of the interrupting speech of the called telephone terminal, the speech-path switch re-establishes the first speech-path between the subscriber's line of the mobile device and the trunk.
A position of the subscriber's line, i.e., a position of the input port of the speech-path switch is not fixed in the communication network in which the mobile device is contained. Accordingly, the switching system is required to establish the speech-path in consideration of both, the input port and the output port.
More specifically, the switching system is required to switch the output port for providing the communication service as well as to switch the input port due to movement of the mobile device. Switching of these speech-paths for the different purposed is carried out in the single speech-path switch. As a result, it is necessary to take the servicing state along with the state of the mobile device into account, which complicate the processing in the switching system.